The finding of Upper Paleolithic engravings in 2016 triggered a multidisciplinary investigation of the Alkerdi cave system (Urdazubi, N Spain). The study of the speleogenetic processes led to the identification of at least 6 paragenetic cave levels with associated sedimentary infill. In order to unravel the timing of changes in the karst dynamics and to get some insights about sediment origin, two sediment samples were collected from cave levels 4 and 1 for numerical dating purpose, using both Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) methods. One additional modern-age sample was also taken from the entrance of the karst to evaluate the magnitude of the optical bleaching achieved by the quartz grains before entering the cave system. Last, one sample was collected from a flowstone for U-series dating, providing independent age control.

OSL measurements were carried out using small quartz multi-grain (MG) and single-grain (SG) Single Aliquot Regenerative-dose (SAR) protocol. Initial Equivalent Dose (D_e) results show evidence of saturated OSL signal for the sample of the higher level (with ∼60% of saturated aliquots). Unlike SA data, SG analyses do not meet the usual quality criteria (e.g., relatively high recuperation ratios, only a few grains with useable signal), suggesting that corresponding dating results should be treated with caution.

Hence, both MG and SG TT-OSL and MG ESR methods were subsequently employed, as the corresponding signals are known to have higher saturation levels than OSL ones. ESR analyses were based on the Multiple Centre (MC) approach using the standard multi-grain multi-aliquot additive (MAA) dose method, while TT-OSL measurements were performed following Demuro et al. (2020). The latter, however, did not return any useful results for both samples. MC ESR data show the usual D_e pattern (D_e(Al)>D_e(Ti op. D)>D_e(Ti–H)) indicating that among the three ESR signals analyzed, the Ti–H most likely provides the closest estimate to the true burial age. However, low measurement repeatability and goodness-of-of fit indicate that the reliability of the ESR results may be reasonably questioned.

Results derived from this multi-technique dating approach provide the first chronological constraints for the sedimentary infill of the Alkerdi cave system. In particular, they suggest that sediment deposition in Cave Level 4 (ALK-OSL01) occurred around 130 ka, which is in good agreement with the minimum age constraint given by the speleothem (80.5 ± 9.0 ka). In comparison, the young age obtained for sample ALK-OSL02 (5.0 ± 0.9 ka) suggests recent Holocene formation of the lowest cave level 1.

Finally, the MG De value obtained for the modern sample is close to zero (<1 Gy), indicating that the OSL signal is almost fully reset at a multi-grain level before entering the cave. Additionally, despite the large De overdispersion measured in this modern sample, the De values are one to two order of magnitude lower than those obtained with the same model in the other two samples. Therefore, the large OSL D_e overdispersion (OD) values of up to 64% obtained for the two samples from Cave Level 4 and 1 are most likely related to re-sedimentation processes inside the cave system.

2016 年上旧石器时代雕刻的发现引发了对 Alkerdi 洞穴系统（西班牙北部乌尔达祖比）的多学科调查。对洞穴形成过程的研究导致了至少 6 个共生洞穴水平与相关沉积填充物的识别。为了揭示岩溶动力学变化的时间并获得有关沉积物起源的一些见解，从洞穴 4 级和 1 级采集了两个沉积物样本用于数值测年，同时使用光激发发光 (OSL) 和电子自旋共振 ( ESR) 方法。还从岩溶的入口处采集了一个额外的现代样本，以评估石英颗粒在进入洞穴系统之前所达到的光学漂白程度。最后，从流石中收集了一个样品用于 U 系列测年，

使用小石英多粒 (MG) 和单粒 (SG) 单等分再生剂量 (SAR) 协议进行 OSL 测量。初始等效剂量 (D _e ) 结果显示较高水平样品的饱和 OSL 信号（约 60% 的饱和等分试样）。与 SA 数据不同，SG 分析不符合通常的质量标准（例如，相对较高的回收率，只有少数具有可用信号的谷物），这表明应谨慎处理相应的测年结果。

因此，随后采用了 MG 和 SG TT-OSL 和 MG ESR 方法，因为已知相应的信号具有比 OSL 更高的饱和度。ESR 分析基于多中心 (MC) 方法，使用标准多颗粒多等分添加剂 (MAA) 剂量方法，而 TT-OSL 测量是在 Demuro 等人之后进行的。（2020 年）。然而，后者没有为两个样本返回任何有用的结果。MC ESR 数据显示通常的_De模式 (D _e (Al)>D _e (Ti op. D)>D _e(Ti-H)) 表明在分析的三个 ESR 信号中，Ti-H 最有可能提供最接近真实埋葬年龄的估计。然而，低测量重复性和拟合优度表明 ESR 结果的可靠性可能受到合理质疑。

从这种多技术测年方法得出的结果为 Alkerdi 洞穴系统的沉积填充物提供了第一个时间限制。特别是，他们认为洞穴级别 4 (ALK-OSL01) 的沉积物沉积发生在 130 ka 左右，这与 speleothem 给出的最小年龄限制 (80.5 ± 9.0 ka) 非常吻合。相比之下，样品 ALK-OSL02 (5.0 ± 0.9 ka) 获得的年轻年龄表明最近全新世形成了最低洞穴级别 1。

最后，现代样品获得的 MG De 值接近于零（<1 Gy），表明 OSL 信号在进入洞穴之前几乎完全重置为多粒级。此外，尽管在这个现代样本中测量到很大的 De 过度分散，但 De 值比在其他两个样本中使用相同模型获得的值低一到两个数量级。因此，从洞穴 4 级和 1 级的两个样品中获得的高达 64%的大 OSL D _{e过度分散 (OD) 值很可能与洞穴系统内的再沉积过程有关。}